Figure 1 - uploaded by Marcos Perez
Content may be subject to copyright.
Source publication
Cold rotary forging is an innovative incremental metal forming process whose main characteristic is that the workpiece is only partially in contact with a conical tool, reducing therefore the required forging loads. However, in spite of many benefits of such a process, wide industrial implementation of rotary forging is not possible without proper...
Contexts in source publication
Context 1
... these bars, cylindrical hollow preforms with dimensions of 100 × 200 (length) × 7.5 mm (thickness) were machined along the rolling direction. Figure 1 shows both the initial preform and the final rotary forged component analyzed in the present paper. This figure also indicates the rotary forging reference system, where ND (normal direction), TD (tangential direction) and ED (external direction) represent the axial/feed direction, the flange stretching along the circumferential direction, and the direction of lateral expansion of flange (increase of external diameter), respectively. ...
Context 2
... a slight but constant reduction in hardness can be observed at middle and bottom positions along the flange, especially close to the flange edge/nose. Note that the flange formation requires a significant increase in the external diameter during the rotary forging process, from 100 mm in the preform to up to 165 mm at the end of the rotary forging process (Figure 1). This results into high levels of hoop (transverse) strain to be accommodated in the flange. ...
Context 3
... impact of rotary forging on Jethete M152 microstructure was also analyzed in transverse orientations at four different positions (sections AB, BC, CD & DE) as shown in Figure 11. A distance of 1 cm among consecutive sections was also considered. ...
Context 4
... results are in agreement with the hardness results (Figure 6), where two peaks of hardness were found. The microstructure of section AB (Figure 12.a) is characterized by a strong reorientation of cold-worked martensite along the transverse direction. As commented before, a large amount of deformation is required to accommodate the increasing external diameter as the rotary forging process proceeds. ...
Context 5
... commented before, a large amount of deformation is required to accommodate the increasing external diameter as the rotary forging process proceeds. In the case of the section DE ( Figure 12.d), localized shear deformation on the surface can be observed aligned also along the transverse direction. This latter feature is associated with the relative movement of the upper tool against the preform, together with the large friction forces which act on the final stages of the rotary forging process. ...
Context 6
... results into the accumulation of compressive stresses in the transition region between the flange and the straight region. These results also explain both the peak in hardness (Figure 6) and the localized shear deformation (Figure 12.d) observed in this region. ...
Context 7
... there is a point in which the resultant compressive force exceeds the critical buckling load, leading to the occurrence of the axisymmetric buckling phenomenon, and determining the cold formability limit of the flange. Figure 13 shows macrographs of flange sections (Part A, B) in the as-heat treated condition. Similar features as those previously observed in as-forged condition (Figure 8) are detected. ...
Context 8
... the cold-worked martensite has been fully replaced by tempered martensite, where no differences along the full component were found, in agreement with the hardness results (Figure 7). This latter observation is also confirmed by Figure 14, where micrographs were taken in those positions depicted in Figure 13. Homogeneous structures and grain size distributions can be found across the whole component, regardless of either the prior deformation or position across the thickness, and despite the large differences previously found in as-cold formed condition. ...
Context 9
... the cold-worked martensite has been fully replaced by tempered martensite, where no differences along the full component were found, in agreement with the hardness results (Figure 7). This latter observation is also confirmed by Figure 14, where micrographs were taken in those positions depicted in Figure 13. Homogeneous structures and grain size distributions can be found across the whole component, regardless of either the prior deformation or position across the thickness, and despite the large differences previously found in as-cold formed condition. ...
Context 10
... the as-rotary forged condition, Figure 15 plots the engineering stress-strain curves from samples obtained in different positions and orientations, as shown in Figure 5. Comparing the stress-strain curves from specimens located at the straight region (see Figure 15.a): Position No.2 (transverse orientation) vs. No.4 (axial orientation), identical stress-strain curves were found. ...
Context 11
... the as-rotary forged condition, Figure 15 plots the engineering stress-strain curves from samples obtained in different positions and orientations, as shown in Figure 5. Comparing the stress-strain curves from specimens located at the straight region (see Figure 15.a): Position No.2 (transverse orientation) vs. No.4 (axial orientation), identical stress-strain curves were found. ...
Context 12
... the case of those specimens located in the flange (Positions No. 1, 3 & 5), strong differences in the engineering stress-strain curves were observed as a function of both the orientation and position (Figure 15.b). Those samples located at position No.3 (flange edge, transverse direction) present the highest strength levels with the lowest elongation values. ...
Context 13
... differences can be explained by the large hoop strains introduced to accommodate the increasing external diameter of the flange, the transverse samples being aligned to this direction. Figure 16 plots the evolution of yield stress (ys) and ultimate tensile strength (Ult) on the stress-strain curves of the transverse samples (Positions 1, 2 &3). In this case, only 1 stress-strain curve per position is plotted for the sake of clarity. ...
Context 14
... differences can be explained by the large hoop strains introduced to accommodate the increasing external diameter of the flange, the transverse samples being aligned to this direction. Figure 16 plots the evolution of yield stress (ys) and ultimate tensile strength (Ult) on the stress-strain curves of the transverse samples (Positions 1, 2 &3). In this case, only 1 stress-strain curve per position is plotted for the sake of clarity. ...
Context 15
... this case, only 1 stress-strain curve per position is plotted for the sake of clarity. Figure 17 shows the fracture surface of the tensile samples from positions No.2 and 3, which represent those regions with minimum (0, annealed martensite) and maximum deformation (cold-worked martensite). However, no differences in the (dimpled) fracture surface were found between both specimens, in agreement with the similar post- uniform elongation values obtained across the whole component. ...
Context 16
... elongate as they grow, and the ligaments of the matrix material between the voids become thin, therefore, the final stage of ductile fracture is coalescence through the separation of the ligaments that link the growing voids. In the as-heat treated condition, engineering stress-strain curves from samples located at different positions and orientated in different directions (transverse vs. axial) are plotted in Figure 18. From these figures it is quite clear that all the tensile specimens depict the same engineering stress-strain curves, regardless the position and orientation, or in other words, regardless the prior history. ...
Context 17
... 8.7-9.3 %, respectively, with reductions in area of 51.2-53.8%. This results are in agreement with hardness ( Figure 7) and microstructural analysis results (Figure 13), in term of isotropic and homogeneous final properties. Finally, Figure 19 depicts the dimpled fracture surface of tensile samples from positions No. ...
Similar publications
This paper presents a comprehensive study of the tensile performance, heat treatment, fracture, decrease of residual stress, second-phase particle and microstructures of a 316L stainless steel fabricated by directed laser deposition (DLD) and thermal milling (starting milling temperature at 250 ± 50 °C), a typical hybrid additive and subtractive ma...
Citations
... Several researchers have studied this process mainly focusing on process modelling and microstructural evolution. For example, studies have focused on modelling the cold rotary forging of alloy steels and its varying mechanisms [2,3] as well as to understand material behaviour during the flaring process [4]. Besides the steels, the nickel-based alloys such as C263 and Inconel 718 (IN718) have attracted research in this area due to its widespread application in manufacture of aero engine components. ...
C263 and Inconel 718 are precipitation hardenable nickel-superalloys widely used in different sections of a gas turbine engine dependent on their strength and temperature capability. Cold rotary forging is an effective route for manufacturing axisymmetric components with significantly higher material utilisation as compared to machining from conventional hot forgings. This paper presents a study on how C263, an alloy system strengthened by γ’, and Inconel 718, an alloy system strengthened by γ” and δ, deform during the cold rotary forging process and how their microstructures evolve. The two alloys exhibit maximum formability in solution-annealed condition. In this study, both C263 and Inconel 718 were annealed before the cold rotary forging operation. Parts with a 90° bend flange were successfully cold rotary forged from tubular preforms with a wall thickness of 6 mm. For both the alloys, the cold rotary forged parts exhibit significant differences in material properties from the undeformed sections to the most deformed section (i.e. the flanges). Post-forging heat-treatments are required to impart the desired material properties throughout the part. Therefore, appropriate annealing and aging treatments were identified for each of the two alloys. These heat-treatments led to uniform material properties for both deformed and undeformed sections of the cold rotary forged flanges in case of both the alloys.
... In cold-worked structures, the increase in strength properties is accompanied by loss of ductility and toughness. The strong texture developed in the course of this process means that the properties of the final components are strongly dependent on the orientation (anisotropic properties) (Pérez, 2017a). ...
Rotary forging is an attractive incremental metal forming with many advantages over any other processes, requiring smaller deformation force and providing high accuracy (near-net-process). The main applications of rotary forging process include families of bevel and helical gears, and flanged components for transmissions such as disk, rollers, wheels, etc. The main aim of this work is to study the impact of rotary forging process on the microstructural and texture evolution of high-strength materials, and martensitic stainless steels in particular, during cold rotary forging process. Jethete M152 alloy is a cold formable 13%-Cr martensitic stainless steel used in the aerospace industry. Jethete M152 flanged test-pieces were rotary forged at room temperature. The process was interrupted at 4 intermediate steps, providing flange reductions of 25, 30, 50, 65 and 70%. A complex grain flow and inhomogeneous deformation patterns are developed during rotary forging, characterized mainly by the formation of a strong deformation band which run parallel to the bottom die. A transition from asymmetrical bulging (inverted mushroom) to symmetrical bulging was observed as a result of the initial lower contact area of the preform with the bottom die. From microstructural analysis by EBSD, the lath structure of Jethete M152 is gradually reoriented and changes it shape in a direction parallel to the compression plane, developing a lamellar/pancake structure in those positions with maximum deformation. These microstructural changes are accompanied with the development of a strong texture formed by a duplex <100> + <111> fibers aligned with the compression axis, being the <111> fiber the stronger one. These findings are in good agreement with uniaxial compression for bcc metals. The analysis of the Orientation Distribution Figures (ODF) reveals that 4 main texture components are formed in the course of the rotary forging process: Brass {110}〈112〉, L {110}〈110〉, I {112}〈110〉, and Cube {001}〈100〉. In contrast with reported literature for bcc metals, no texture component associated to the γ-fiber ({111} ‖ ND) was found.
The article discusses the process of cold axial rotary forging of tube blanks with a conical roller. The process of forming the inner flange is analyzed. During the analysis, possible variants of the technological process depending on the geometric parameters of the workpiece were determined. Possible defects in the formation of the inner flange have been identified and described. A comparison is made in the formation of the flange during rotary forging using a fixed and movable dies. The research method was based on finite element computer modeling in the “Abaqus” software package. It made possible to determine the technological parameters of the process and the geometric dimensions of the workpiece, at which it is possible to obtain defect-free parts with an internal flange.Keywordsrotary forginginternal flangetube blankconical rollsimulationmovable die
A study of PVD coatings, solid-in-liquid suspensions and ashless phosphate esters at the upper die-workpiece interface when rotational rotary forging martensitic steel. The aim was to gain tribological insight for advanced near net-shape process development. The test method was a cylinder upsetting operation in an industrial-scale press. Carrier liquid vaporisation resulted in lower torque when aqueous rather than oil-based dispersions were employed. However, oil-based dispersions generated superior workpiece surface finish, and there was a positive correlation between torque and through-thickness homogeneity of deformation. A tribological synergism occurred when MoS2 micro-platelets and ashless phosphate esters were mixed in mineral oil. This lubricant achieved higher quality surface finish and greater protection against adhesive wear than did each component dispersed separately in oil.
